The present invention generally relates to control pilots and pressure management systems, such as those employed on municipal water utility systems. More particularly, the present invention relates to an adjustable hydraulically operated pilot assembly to manage system pressure conditions.
The supply and pressure control of water mains and municipal water utility systems and the adequacy of the supply and supply infrastructure vary from place to place. Conventionally, the water system is arranged so that a minimum water pressure is maintained at all points in the system. This is usually done with reference to the pressure prevailing at a number of critical points, including those which are highest above sea level or farthest away from the source of supply in the water district. However, there is invariably considerable fluctuation in the demand for water throughout the day and also a considerable seasonal variation so that the maximum pressure is generally higher than the necessary minimum value.
There is a general understanding throughout the worldwide water supply industry that instances of water loss are common in many water distribution networks and in many instances the level of water loss can be relatively high. The amount of water loss in the system is due to a variety of leak sources, such as improperly tightened pipe flange connections, leaking flange gaskets, leaking valve seals, failed seals, old pipes (with pinhole bursts), loose fittings, leaky faucets, etc. The sum of these sources of leakage can add up to a substantial amount of water loss. Maintaining the entry point pressure at all times at the level necessary to provide adequate pressure at the distant points for periods of high demand can result, during periods of low demand, an excessive pressure at the consumer's premises, and thus increased waste of water by unnecessary consumption and leakage. The volume of water lost through leakage is directly related to pressure in the system.
Automatic pressure reducing valves are used in water distribution systems to reduce pressure to a pre-determined value or sub-point that is adequate, but does not expose normal components, such as household hot water tanks, to overpressure. The sub-point is typically determined to provide minimum pressure that meets criteria of the water utility, particularly under maximum or “peak” demand conditions which can occur when a fire is being fought. The pressure required for peak demand is usually significantly higher than that required for “off-peak” or typical nighttime conditions. Under low demand conditions, not only does leakage form a higher proportion of the total demand, but investigation has implied that some leak orifices can actually increase in area with pressure, aggravating the problem if excessive pressures are maintained at all times.
Thus, in the waterworks industry, there is a desire to lower the system water pressure during low demand periods. From a practical point of view, lowering the water pressure in a system during a low demand period reduces the amount of water loss due to system leaks. Managing water pressure can also reduce the incidence of pipe breaks in aging water network infrastructures. A lower pressure means pipes are subject to lower stresses during low demand periods. Over time, the cumulative lower stresses to piping infrastructure helps to increase the life expectancy of the piping in the water distribution system.
Accordingly, there is a continuing need for an adjustable hydraulically operated pressure management control pilot assembly which can be used to set the water pressure high and low points so as to control the system water pressure between low demand periods and high demand periods. There is also a continuing need for an improved flow-driven valve system for automatically controlling downstream pressure between selected set points. The present invention fulfills these needs and provides other related advantages.